Conventionally, a ship is known having an engine, an outdrive device having a propeller rotated by power of the engine, and a clutch engaging and disengaging power transmission from the engine to the propeller (for example, see the Patent Literature 1). The ship described in the Patent Literature 1 is constructed so that the engine is rotated at a low idling rotation speed so as to rotate the propeller at a low speed, whereby sailing at a low speed (so-called troll sailing) is performed.
However, according to the art described in the Patent Literature 1, the troll sailing by slipping the clutch (so-called semi-clutch) cannot be performed. Namely, sailing with a sailing speed lower than the sailing speed at the low idling rotation speed of the engine cannot be performed, whereby the sailing speed may be too high so as to make the maneuvering of the ship difficult for some operators. For example, at the time of berthing and unberthing of the ship, the sailing speed may be too high so as to make the operation of the berthing and unberthing of the ship difficult for an unskilled operator unfamiliar to the maneuvering of the ship.